The present invention relates generally to seals for use with rotary or reciprocating shafts, particularly to seal cages used in such seals.
Injected sealing compound systems have been introduced as an alternative to expensive mechanical seals used with rotating shafts or braided compression packing used with rotating or reciprocating shafts, e.g., in pumps, compressors, or other apparatus. Unlike mechanical seals and braided compression packing, injectable sealing compounds are self-lubricating, eliminate leakage, need no cooling water or flush water, and do not damage shaft sleeves. Injectable sealing compound systems therefore can substantially reduce or eliminate flush water consumption and equipment maintenance, resulting in substantial savings. See, e.g., Glowacki, xe2x80x9cMills Use New Sealing Compound to Minimize Water Consumption,xe2x80x9dPulp and Paper, Nov. 1995, 97-98.
In an injectable sealing compound system, a stuffing box provided with a fluid injection port surrounds a rotating or reciprocating shaft that extends through the stuffing box bore. A sealing means (e.g., braided packing rings, gasket rings, restriction bushing, taper rings) concentrically surround the shaft at opposite ends of the stuffing box bore. The space between the packing seal rings is filled with an injectable sealing compound that is injected under greater than atmospheric pressure into the stuffing box through an injection port. The packing rings or other sealing means depend on the injectable sealing compound to hold them in place.
Leakage of the injectable sealing compound from the stuffing box can cause the packing seal rings or other sealing means to move toward each other. If one of the packing seal rings blocks or moves past the injection port, it is necessary to shut down the machinery and reposition the rings before resealing. If a packing seal ring opens up at its joint, sealing compound can escape from the stuffing box.
The present invention provides an apparatus that is useful as a spacing device, e.g., a seal cage or lantern ring for a seal or compression packing associated with a shaft. Embodiments of the invention can be used, for example, in injectable sealing compound systems, for which previous seal cage designs are illsuited.
According to one embodiment of the invention, the apparatus includes rails that are adapted to be disposed in an annular configuration around a shaft in laterally spaced positions to contain an injectable sealing compound in a space defined between the seal cage and the shaft. Each rail includes brace towers that are spaced apart longitudinally along the rail and connected by connector elements. In some embodiments of the invention, the connector elements are connected to the brace towers nearer to the end of the second projecting portion (projecting away from the shaft) than to the first projecting portion. At least one brace element is attached to the brace towers of the rails and extends between the rails to maintain lateral spacing between the rails.
The brace towers each include a first projecting portion that projects toward the shaft and a second projecting portion that projects away from the shaft. In at least some embodiments, brace towers on one rail are laterally aligned with brace towers on the other rail with brace elements or cross braces extending between the aligned brace towers. Thus, each brace element extends from a respective brace tower of one rail to a corresponding brace tower of the other rail.
There are a plurality of openings between the rails of a sufficient size to permit an injectable sealing compound to flow through the openings and into the space between the seal cage and the shaft. Preferably, the openings occupy from about 50 to 90 percent or more of the area defined between the rails.
According to another embodiment of the invention, a brace element has an elongate element at one or both ends of which is a head portion that is adapted to bear against and project outwardly from one side of a first rail (the side facing away from the second rail), and a shoulder spaced inwardly from the end of the brace element and adapted to bear against the other side of the first rail (the side that faces toward the second rail), thereby restricting lateral movement of the first rail relative to the second rail.
According to another embodiment of the invention, a land is positioned between adjacent brace towers. The land projects away from the shaft when the rails surround the shaft.
According to another embodiments of the invention, the brace element(s) is releasably attached or mounted to the brace towers. For example, in one such embodiment, respective brace towers of the two rails are each provided with a slot sized to receive an end portion of a brace element. The spacing between the rails, and thus the xe2x80x9cwidthxe2x80x9d of the apparatus, can therefore be adjusted for use with a wide range of stuffing box depths by selecting brace element(s) of an appropriate length.
According to another embodiment of the invention, the length of the rails, and thus of the seal cage, is adjustable to permit the seal cage to be adapted for use with shafts of different diameters. For example, the rails (or the entire apparatus) can be made of a material that can be cut. Alternatively, short lengths of a rail or assembled seal cage portions can be linked together to form longer rails or seal cages. Various link arrangements are discussed below. For example, in a xe2x80x9csplit railxe2x80x9d linking arrangement, each end of a rail (or adjoining ends of two rail sections) is provided with a rail end portion or partial brace tower. When a rail end portion of one section of rail is aligned with a complementary rail end portion of another section of rail, the rail end portions of the two sections together define a brace receptacle that releasably holds a brace element (e.g., an end portion thereof), thereby connecting the two rail ends. This xe2x80x9csplit railxe2x80x9d linking arrangement can be used to connect two ends of a single rail, holding the rail in an annular configuration or joining two rail portions, for example. Alternatively, one or more linking elements can be attached to brace elements of ends of a seal cage (or seal cage portions).
A seal cage according to at least some embodiments of the invention can be can be assembled from several parts, including, for example, rails and brace elements. Accordingly, seal cages according to such embodiments can be provided as a kit that includes, for example, rails having brace towers of different heights, braces of different lengths, linking elements, etc. Alternatively, one-piece (i.e., monolithic) seal cages are also provided. For example, one-piece embodiments can be injection molded in a closed, annular configuration, or in an open (e.g., flat, linear) configuration such that the apparatus can be curved about a central axis to assume an annular configuration for installation.
According to another embodiment of the invention, the seal cage retains an injectable sealing compound in the space between the seal cage and a shaft without a sealing means exterior to the rails, e.g., packing seal rings, braided compression packing, gasket rings, restriction bushings, taper rings, or other conventional sealing means.
Use of an injectable sealing compound system including a seal cage according to the invention results in lower total material and operation costs and substantially lower water consumption (since flush water can be eliminated) as compared with standard compression packing or mechanical seals.
The foregoing and other features and advantages of the invention will become more apparent from the following detailed description and accompanying drawings.